A growing body of evidence strongly suggests that neuroblastomas are highly dependent on the development of a robust vascular supply during malignant evolution and establishment of disseminated disease. Thus, we hypothesize that neovascularization is a critical component of high-risk neuroblastoma biology and that angiogenesis inhibition will be an effective adjuvant to conventional treatment. In order to prioritize antiangiogenic compounds and strategies for future clinical trials, it is first necessary to define and validate the specific angiogenesis-related genes and pathways that are most commonly altered during neuroblastoma disease progression. This will allow for the rational selection of targeted antiangiogenic compounds for the treatment of human neuroblastoma. Accordingly, in Aim 1 we propose to define the differential and temporal expression patterns of relevant angiogenesis-related genes critical to neuroblastoma neovascularization. We plan a series of gene expression profiling experiments in patientderived archival tumor samples and in a tractable transgenic mouse model of human neuroblastoma to define the genes and pathways critical to angiogenesis and metastasis formation. Gene expression data will be experimentally verified in order to prioritize candidate targets for further investigation. In Aim 2 expression profiling data will be functionally validated at the protein level and in vivo using the transgenic neuroblastoma model. Important signaling pathways defined in Aim 1 will be targeted using small molecule inhibitors. Tumor response patterns will be correlated with imaging, molecular and histopathologic markers of biological efficacy. In addition, angiogenesis genes showing differential expression related to tumor phenotype in Aim 1 will also be validated for clinical relevance in an independent group of representative neuroblastoma primary tumor samples. In Aim 3 we will determine the optimum strategy for incorporating antiangiogenic therapy into current treatment regimens using preclinical models of neuroblastoma. Effective antiangiogenic agents defined in Aim 2 will be tested for synergistic interaction with cytotoxic (chemotherapy or targeted radiotherapy) and noncytotoxic (Trk tyrosine kinase, other anti-angiogenesis inhibitor and retinoid) agents in order to determine optimal integration into overall patient treatment strategies. This project should shed significant insight into the vascular biology of human neuroblastoma. Successful completion of this project may lead to the development of novel treatment strategies for high-risk neuroblastoma patients that could translate into improved cure rates with significantly less short- and long-term toxicity.